XXII ISPRS Congress 2012: Technical Commission VII

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Multivolume work

Persistent identifier:: 1663813779

Title:: XXII ISPRS Congress 2012

Sub title:: Melbourne, Australia, 25 August-1 September 2012

Year of publication:: 2013

Place of publication:: Red Hook, NY

Publisher of the original:: Curran Associates, Inc.

Identifier (digital):: 1663813779

Language:: English

Additional Notes:: Kongress-Thema: Imaging a sustainable future

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Document type:: Multivolume work

Volume

Persistent identifier:: 1663821976

Title:: Technical Commission VII

Scope:: 546 Seiten

Year of publication:: 2013

Place of publication:: Red Hook, NY

Publisher of the original:: Curran Associates, Inc.

Identifier (digital):: 1663821976

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(39,B7)

Language:: English

Additional Notes:: Erscheinungsdatum des Originals ist ermittelt.; Literaturangaben

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 22., 2012, Melbourne; International Society for Photogrammetry and Remote Sensing

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2019

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [VII/2: SAR INTERFEROMETRY]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: TOWARDS AN URBAN DEM GENERATION WITH SATELLITE SAR INTERFEROMETRY Cristian Rossi, Thomas Fritz, Michael Eineder, Esra Erten, Xiao Xiang Zhu and Stefan Gernhardt

Document type:: Multivolume work

Structure type:: Chapter

, 2012 International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 XXII ISPRS Congress, 25 August - 01 September 2012, Melbourne, Australia TOWARDS AN URBAN DEM GENERATION WITH SATELLITE SAR INTERFEROMETRY Cristian Rossi^, Thomas Fritz^, Michael Eineder^, Esra Erten^, Xiao Xiang Zhu® © and Stefan Gernhardt® “German Aerospace Center (DLR), Remote Sensing Technology Institute (IMF), Wessling, Germany ¢ cristian.rossi@dlr.de bIstanbul Technical University (ITU), Civil Engineering Faculty, Department of Geomatic Engineering, Maslak Istanbul, Turkey “Technical University Munich (TUM), Remote Sensing Technology (LMF), Munich, Germany Commission VII/2 KEY WORDS: SAR, Interferometry, TanDEM-X, Urban Digital Elevation Models ABSTRACT: This paper analyzes the potentials offered by the TanDEM-X mission for the generation of urban DEMs. Operationally acquired urban Raw DEMs are validated using as reference a LIDAR DEM. The approach used for the validation is application-oriented as a sub- product is a derivation of a urban volume map. The mean buildings absolute height error is found to be below 5 meters. Neglecting the buildings geolocation errors, this value drops below 60 centimeters. Nevertheless, the operational municipal mapping is limited to the standard resolution of 12 meters. The limitation is attenuated with the use of high resolution spotlight data. High-resolution raw DEMs over Las Vegas and Berlin are first analyzed. Some modifications to the interferometric processing chain necessary to produce high quality DEMS are studied. The obtained results open a new perspective to the urban DEM generation with satellite SAR interferometry. 1 INTRODUCTION The mapping of urban areas is a claimed task for many manage- ment applications, such as urban development monitoring, urban climate studies, and renewable energy surveys. Airborne data are widely used at this purpose for the generation of Digital Elevation Models (DEMs). LiDAR (Light Detection And Ranging) is a ma- ture technology for obtaining DEMs in urbanized environment. Spaceborne Synthetic Aperture Radar (SAR) is on the contrary not largely exploited due essentially to the lack of suitable data. In fact, an essential prerequisite for a successful exploitation of SAR data finalized to urban reconstruction is a resolution capable to map the desired target. A second one, but not less important, is the absence of temporal decorrelation in between the two SAR acquisitions, or, in other words, an interferometric bistatic config- uration. The TanDEM-X mission, started in June 2010, has as pri- mary objective the generation of a global DEM following the high standard accuracy HRTI-3. The X-band sensors employed for the mission allow an accurate building mapping, hence accomplish- ing the first prerequisite. Additionally the mission constitutes the first bistatic SAR interferometer in space, letting to a faithful sur- face reconstruction free of atmospheric and temporal decorrela- tions. The acquisition mode used to achieve the HTRI-3 require- ments is the stripmap one, with a final spatial DEM resolution of 12 meters. This resolution does not assure an accurate mapping of dense metropolitan areas, nevertheless semi-urban and indus- trial areas are well mapped as shown in Sec. 2 with a validation made using reference LiDAR data over Munich (Germany). The mission foresees however experimental spotlight acquisitions fi- nalized to the generation of higher resolution DEMs following the HRTI-4 standards with a 6 meters spatial resolution. Considering this resolution, a denser urban mapping becomes then possible. First examples of urban experimental high-resolution DEM are shown over Las Vegas (USA) and Berlin (Germany) in Sec. 3. The processing chain adopted for the interferometric DEM gen- eration, also called Raw DEM, is built in the Integrated TanDEM- X Processor (ITP). Although the chain is highly optimized in a global scale, some modifications are necessary for the purposes of the paper. In particular, the spectral shift filtering, the coreg- istration, the interferogram generation and the phase unwrapping 73 processing steps are redesigned towards an optimal configuration for the local municipal zone to map. The limits of an interfero- metric SAR city modelling are introduced in Sec. 4 as conclusive remark. 2 OPERATIONAL URBAN RAW DEM VALIDATION The main goal of the TanDEM-X mission is the generation of a global DEM, thus including all the cities all over the world. The processing of Raw Data for the generation of the Raw DEM is performed by one single processor, the Integrated TanDEM- X Processor (ITP) (Breit et al., 2010), not described in this pa- per. ITP is optimally configured in every single processing stage to provide a Raw DEM close to the HRTI-3 standards (relative point-to-point height accuracy of 2 meters for moderate terrain with slope inferior to 20° in a 1° by 1° cell). In the processing facilities, for a standard 50 by 30 kilometers scene, the processing time required for the generation of the Raw DEM from the Raw Data is about 15 minutes. This high optimization follows the al- gorithms presented in (Fritz et al., 2011). Cities inside the scene are mapped at the standard posting of 12 meters. Even if the rel- ative TanDEM-X height accuracy requirements are successfully accomplished (Rizzoli et al., 2012), they are too coarsely defined for urban zones. The cell used for the DEM height error spec- ification is too large for an accurate analysis over a single city. A new strategy is then adopted for the validation of the abso- lute height of isolated buildings inside the DEM. It is based on the comparison between detected buildings in a reference LiDAR DEM and the TanDEM-X one. The input for the comparison is the Digital Buildings Model (DBM), derived through a difference between the DEM and its Digital Terrain Model (DTM). In prin- ciple a thresholding operation on the DBM would be sufficient to detect the buildings. In practice, due to the interferometric er- rors intrinsic to the urban DEM generation, such as geometric decorrelations or phase unwrapping issues (Rossi et al., 2011), a thresholding is not sufficient and a morphological operation, nec- essary to detect the underlying structures, is used. The simplest structuring element for the morphological operation is the 2-by- 2 square. By this way sharp rectangular edges representing the buildings - are extracted and noisy areas are discarded. Standard

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